Isn't it cheaper to cool a datacenter in a more temperate/cool region than one that has a 9-month-long summer?

Why would anyone want to go to Texas to build a datacenter and worry about the cooling, when they could pick any other state?

Because the other big expense in a datacenter: electricity. Texas has really cheap electricity compared to the rest of the country, sitting at second cheapest after North Dakota.

Long summers = tx actually has lots more Solar, but also biz friendly laws, biz friendly taxes, lots of corp HQ, cheap land, own power grid (for better or worse), cost of labor, etc.